Interest grows in unusual Egyptian method of mosquito control

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Somalia and South Sudan are keen on using the technique to cut malaria

It uses chlorophyll powder and sunlight to kill mosquito larvae

But there are reservations about large-scale implementation

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[CAIRO] Plans are progressing to introduce an unusual method of mosquito control which involves sprinkling powdered plant extracts on swampy mosquito nurseries. The Egyptian researchers behind the innovation have set up a company to develop the method and recently signed an agreement with South Sudan’s government to implement the technique there.

The researchers, whose firm is called InRaD (Innovative Research and Development), tell SciDev.Net that they have also had requests from Somalia’s health ministry to do the same.

Later this month, Mahmoud Abdel-Kader, a photochemist at the German University in Cairo, Egypt, and one of the two scientists behind the technique, is due to fly to Switzerland to present the results of laboratory and field research to the WHO. He says he is planning on discussing the possibility of WHO approval of the method.

“The innovative method utilises the rays of the African sun to contain the disease.”

El-Tayeb, Cairo University

The technique involves adding a derivative of the plant pigment chlorophyll to wetlands infested with the aquatic larvae of mosquitoes.

Abdel-Kader’s collaborator, Tarek El-Tayeb, a biologist at Cairo University, says: “We extracted the chlorophyll from green plants and transformed it into a powder which was sprinkled in places where the larvae are found.

“The larvae climb to the surface of the water for oxygen. Then they feed on the powder, which has been manufactured to float on the surface.”

In plants, El-Tayeb says, chlorophyll absorbs sunlight and passes on its energy so that plants can build their sugary fuels from carbon dioxide. But in its powdered form, the chlorophyll instead transfers the sun’s energy to dissolved oxygen inside the larvae. The resulting form of oxygen is unstable and so reacts with the cells’ components, damaging them and ultimately killing the larvae.

The research included three years of laboratory work as well as field experiments in the wetlands of Ethiopia, Sudan and Uganda that are full of malaria-transmitting mosquitoes. The technique killed between 85 to 100 per cent of larvae, according to a poster summary published in Malaria Journal in 2012.

As well as the Anopheles mosquitoes that are a vector for malaria, the technique kills the Aedes mosquito, which pass on dengue fever. And it kills the Culex mosquito, which transmits parasitic worms that cause a disease called filariasis.

“The innovative method utilises the rays of the African sun to contain the disease,” says El-Tayeb. “It’s a natural method that causes no environmental damage.”

For instance, the Uganda experiments showed no effect on the natural predators such as dragonfly larvae that feed on mosquito larvae.

Muhammad Raja’i, an entomologist at the National Centre for Research in Egypt, tells SciDev.Net that, compared with other biologically safe techniques, this method is “less expensive and more effective at exterminating mosquitoes”.

But there are concerns about its practical application.

Abd al-Majid al-Gharib, a physical chemist at Cairo University, tells SciDev.Net: “I am confident the idea is successful on a small scale, but deploying the powder on every canal, drainage ditch and wetland to control malaria [would be] extremely difficult.”

Yet El-Tayeb says: “The powder is effective for 21 days and the extraction process itself is not expensive at all. We should consider large-scale implementation.”